1. Field of the Invention
The present invention relates to an image pickup apparatus provided with a flash device.
2. Description of the Related Art
In recent years, image pickup apparatuses are widely used. As the image pickup apparatus, for example, there are a photographic camera using a photographic (silver salt) film, and a digital still camera using a CCD image sensor or the like. Many of the image pickup apparatuses have a built-in flash device so as to be photographable under a circumstance lacking a light amount, for instance, under an indoor circumstance. As the photographic film used in the photographic camera, is most employed a color negative film of a daylight type for the purpose of taking a picture in the diurnal outdoors. The color negative film of this type is easily obtained. Further, in recent years, the color negative film has high sensitivity without deteriorating image quality thereof. The photographic film having high sensitivity of ISO 1600, for example, tends to be usually employed.
When flash photographing is performed by using the photographic camera under the dark circumstance, for instance, under the indoor circumstance, a proper exposure amount is obtained by a flash light relative to a main subject of a comparatively short distance, whereas there arises a problem in that the background, which is not affected by the flash light, becomes dark. Recently, however, the background is adapted to have a proper exposure amount in virtue of a clear taking lens, which has a small f-number and is easily used.
By the way, under the photographic circumstance using the flash light, an artificial light source is usually provided for illumination. As to a kind of the light source usually employed, there are a tungsten light source having low color temperature, a fluorescent lamp having a color of a light bulb, and so forth. Meanwhile, in the flash device of the camera, the color temperature of the flash light is set so as to obtain a proper color balance when the flash photographing is performed with the photographic film of the daylight type.
Owing to this, when the flash photographing is performed under the photographic circumstance of the room and so forth, a main subject of a comparatively short distance has an illumination effect of the flash light. Moreover, exposure is carried out mainly by the flash light so that the proper color balance is obtained relative to the main subject. However, with respect to the background which is not affected by the flash light, the exposure is carried out by the illumination light of the available light having low color temperature so that the color balance usually deteriorates.
When a color of the main subject is faithfully reproduced on a photo print produced from the photographic film exposed such as described above, the light-source color of the illumination light greatly remains on a background portion of the photo print so that an orange color is strongly applied thereto. Meanwhile, when the background is corrected in a printing process so as to faithfully reproduce the subject color, cyan is applied to the main subject. Consequently, as the whole of the taken picture, it is impossible to obtain a photo print having good color balance.
When the flash photographing is performed under the photographic circumstance such as described above, only way for improving the color balance of the whole picture is to reduce a color-temperature difference between the illumination light and the flash light. A professional photographer lowers the color temperature of the flash light by attaching a color-temperature conversion filter to a light-emitting surface of the flash device. It is known that there is a flash device automatically performing an operation substantially same with the function that the color-temperature conversion filter is attached to the light-emitting surface of the flash device (for example, Japanese Patent Laid-Open Publication No. 6-308586 and Japanese Patent Laid-Open Publication No. 7-120816).
However, in the method that the color-temperature conversion filter is attached to the flash device, a flash-light amount is reduced. Consequently, there is a disadvantage that an effective emission distance of the flash light is shortened. Moreover, in this method, the color temperature of the flash light is lowered so that it is required to use a photographic film of a tungsten type. This method is difficult to be adopted by a general amateur photographer and the laity.
In a case that the color-temperature conversion filter is attached to the flash device and the daylight-type photographic film is used, the proper color balance is not obtained for the whole picture. But, it is possible to produce a photo print having satisfactory color balance by correcting the color at the time of the printing process. In this case, however, if the color correction is automatically executed when producing the photo print from the exposed photographic film, the photo print is likely to be yellowish on the whole of the taken picture. This reason is that a printer can not automatically specify the main subject of a portrait and so forth. Hence, the printer can not execute the color correction so as to obtain the proper color balance. With respect to the picture taken in this way, it is impossible to produce the photo print having the satisfactory color balance unless the color correction is manually executed.
In another method for obtaining a picture of proper color balance by using the daylight-type photographic film, a color-temperature conversion filter is attached to a photographic optical system in addition to a flash device. The color-temperature conversion filter attached to the photographic optical system converts a color temperature of the tungsten light source into a color temperature of the daylight. Owing to this method, the photographic film is exposed in the proper color balance regarding both of the main subject and the background portion. Thus, it is possible to produce a photo print in which the main subject and the background are reproduced in suitable colors near to the impression colors. In this method, however, the flash light passes through both of the color-temperature conversion filters so that the light amount is lost in some degree corresponding to one or two steps of a stop, for example. Consequently, there arises a problem in that the effective emission distance of the flash light is extremely shortened.
In view of the foregoing, it is a primary object of the present invention to provide an image pickup apparatus in which a picture having proper color balance is obtained without increasing a light amount of a flash device, even if flash photographing is performed under a photographic circumstance illuminated by an artificial light source.
In order to achieve the above and other objects, the image pickup apparatus according to the present invention comprises a color-temperature conversion filter, which is movable between an insertion position and an evacuation position. The color-temperature conversion filter is placed at a photographic optical path when kept in the insertion position, and is evacuated from the photographic optical path when kept in the evacuation position.
During one-frame exposure, first and second exposures are performed. The first exposure is performed with a flash light in a state that the color-temperature conversion filter is moved to the evacuation position. The second exposure is performed without the flash light in a state that the color-temperature conversion filter is moved to the insertion position.
The image pickup apparatus according to the present invention further comprises a shutter device for opening and closing the photographic optical path. While the shutter device opens the photographic optical path one time, the first and second exposures are respectively performed. The shutter device is preferable to be a lens shutter.
In a preferred embodiment, the second exposure is performed after the first exposure. The color-temperature conversion filter raises a color temperature and satisfies a condition that color-temperature conversion ability Tb [mired] is xe2x88x92130 or less.
Moreover, the image pickup apparatus further comprises a color-temperature measure and a filter controller. The color-temperature measure detects a color temperature of an available light. In accordance with the detected color temperature, the filter controller prohibits the color-temperature conversion filter from moving to the insertion position when performing the second exposure. Alternatively, in accordance with the detected color temperature, the filter controller changes movement timing of the color-temperature conversion filter moving to the insertion position when performing the second exposure.
According to the present invention, both of a main subject and its background may be photographed in a proper color balance even if flash photographing is performed under a photographic circumstance illuminated by an illumination light having a color temperature, which is different from that of the flash light.